The present invention relates to a method and apparatus for providing reference laser beams of light and, more particularly, to such a method and apparatus which is employed for leveling and squaring workpieces such as machine rolls.
U.S. Pat. Nos. 4,062,634; 4,035,085; and, 4,031,629 all disclose rotating laser beam projector devices. In each projector device, a generally horizontal rotating laser beam is produced by projecting a primary laser beam generally upward and then deflecting the beam by 90 degrees within a penta-mirror or pentaprism assembly. The pentaprism assembly is rotated about a vertical axis to cause the horizontal beam to rotate. In the past, some laser projector devices have included a removable pentaprism assembly. With such a projector device, the plane defined by the rotating beam could be aligned with a building structure, for example a wall, and the pentaprism assembly could thereafter be removed to produce a reference line normal to the wall.
U.S. Pat. No. 4,676,598 discloses a laser beam projector device which produces an upwardly extending, stationary reference beam and a rotating reference beam perpendicular thereto. With this laser projector device, pentaprism assembly removal is not necessary since the projector device produces an upwardly extending, stationary reference beam.
It has also been known in the past to employ a laser beam projector, similar to the one disclosed in the '598 patent, in combination with a separate penta-prism assembly for parallel machine roll alignment. In this system, the laser beam projector, which emits stationary and rotating reference beams disposed in a substantially orthogonal relationship with one another, is initially positioned on a machine offset center line. The projector is aligned with the offset center line so that the stationary reference beam lies in a vertical plane with the offset center line, and the rotating reference beam is positioned parallel to a further vertical plane in which a head roll of the machine is positioned. The separate penta-prism assembly is positioned downstream from the projector and is likewise positioned on the offset center line. The stationary reference beam is diverted by the separate penta-prism assembly so as to form an alignment reference beam of light for alignment of a second roll of the machine with the head roll. This system, however, has been found to be disadvantageous because it is difficult and time consuming to properly align the separate penta-prism assembly on the offset center line so that the alignment reference beam and the rotating reference beam are parallel with one another to permit accurate alignment of a second roll with the head roll.
It is seen, therefore, that there is a need for a laser alignment system which can be easily and accurately set-up for purposes such as parallel roll alignment.